1. Field of the Invention
The present invention relates to a load detector for an elevator cage.
2. Description of the Background
An ordinary traction type elevator is composed as shown in FIG. 1 and FIG. 2.
In FIG. 1, one terminal of a cable 2 is connected to a cage 1 and the other terminal of the cable 2 is connected to a counter weight via a sheave 31 of a hoisting machine 3 and deflector sheave 4. The hoisting machine is composed of the sheave 31 and a motor 32. The sheave 31 is driven by the motor 32, and the cable 2 is driven by the traction between the sheave 31 and the cable 2. Eventually, the cage 1 is moved up and down via the cable 2.
As shown in enlarged FIG. 2, the cage 1 moves up and down along guide rails 7 by means of guide devices 6 attached to the cage 1. The cage 1 is composed of a cage frame 1A including a crosshead 1Aa, an upright 1Ab and a plank 1Ac, and a cab 1B mounted in the cage frame 1A. That is, construction of the cage 1 is in effect "doubled" by providing the cage frame 1A around the cab 1B, and the cab 1B is supported by vibration-proof materials 1C such as a rubber. The vibration-proof materials 1C reduce vibration transfer from the cage frame 1A to the cab 1B and improve passenger comfort during travel of the cage 1.
Further, a deformation detector 1D is installed between the cage frame 1A and the cab 1B. The vibration-proof materials 1C is pressed by the load of the cab 1B, and the amount of the deformation of the vibration-proof materials 1C is detected by the deformation detector 1D. The amount of the deformation is transmitted to a calculator 11 in an elevator control panel via a transmitting cable 8, a connector box 91 attached on a shaft wall 9a of a shaft 9, and a transmitter 10. The calculator 11 calculates the load of the cab 1B or the load of passengers on the basis of the amount of the deformation from the deformation detector 1D.
The calculator 11 also calculates a necessary torque to drive the motor 32 so as to move the cage 1 smoothly at the start time, and outputs the torque signal to a drive controller 12. Accordingly, even if the cage 1 is filled with many passengers, the cage 1 does not move down suddenly at the start time when a brake is off. On the other hand, even if the cage 1 has no passengers, the cage 1 does not move up suddenly at the start time. That is, the drive controller 12 applies a necessary torque to the motor 32 before the brake is off so as to move the cage 1 smoothly at the start time.
In the above described traction type elevator, both the cage frame 1A and the cab 1B need a proper strength. It is not easy for the cage 1 to meet both the requirements of the proper strength and the capacity of the cab 1B.
As the efficiency of the hoisting machine 3 improves, the vibration of the cage 1 has been reduced. Therefore, all cages are not required to be constructed in "double" in order to improve comfort of a ride in the cab 1B.
But if the cage 1 has a "single" construction, that is to say, the cab 1B is integrated with the cage frame 1A, the deformation detector 1D can not be installed between the cage frame 1A and the cab 1B. As a result, since a load of the cab 1B can not be detected properly, the elevator has difficulty in controlling the torque applied to the motor 32 at the start time in accordance with change in the load.